are compared and more precise measures of mortality employed, the range is wider still. For example, infant mortality rates range from around 25 in Singapore and Hong Kong to more than 200 in some African countries (the African data for 1960-61).* The significant declines in mortality that have occurred almost universally in the less developed countries are, of course, the primary cause of the accelerated rate of population growth in the postwar years. They have also had some effect on the age structure of the developing areas, an age structure characterized by a much greater share of the population in the school-age and preschool groups than in the advanced countries. (See Table 6.) However, the unbroken history of high fertility has been more influential in shaping the youthful, broad-based pyramid (22, 23). TABLE 6 Share of the School-Going and Prospective School-Going Age Groups in the Total Population of Major World Regions, 1970, United Nations' Medium Projections 0-4 Age Group 5-14 Age Group 5-24 Age Group World Total 13.6 22.8 40.8 Mainland east Asia Other east Asiaa South Asiab 12.8 16.0 16.7 22.6 27.1 25.7 41.3 46.1 43.9 Africa 17.2 26.0 45.3 Latin America 16.6 25.8 44.2 Northern America 10.1 19.9 37.3 Europe Japan 8.0 7.5 16.3 15.2 31.9 34.8 aExcludes Japan. "Excludes Israel and Cyprus. Source: (21, pp. 127-32). The less developed regions also have a somewhat greater share of their population in the school-age and preschool groups today than they did a decade earlier, because the growth of these age groups through the 1960's has exceeded that of the population as a whole. A corollary of this youthful dominance is a much smaller proportion of the population in the working ages, the group which must pay taxes to finance educational programs. This situation is only partly offset by earlier entry into, and later withdrawal from, the work force. *0f African countries with available data, Dahomey, Upper Volta, and Cameroon had infant mortality rates in excess of 200 oer 1.000 live births around 1960-61 (20. mi. pp. 34-36).rcent by 1985.